Ethiopian Geography & the Horn for all freshman Program Students in all university of Ethiopia

1. 3.1. Introduction
The topography of Ethiopia is largely determined by the geologic activities
of the Cenozoic Era.
The uplifting of the Arabo-Ethiopian swell and the subsequent
outpouring, spreading and thick accumulation of Trapean lava have given
rise to an outward sloping highland plateau and mountains.
The major faulting resulted in the division of the plateau into two broad
units and the formation of a great structural valley.
They also formed depressions on which lakes were subsequently created.
Geomorphic processes brought some modification to the structural
landform by river dissection and roughening on the highlands, and
deposition on the lower areas.

2. The Ethiopian landform is characterized by great diversity.
There are flat-topped plateaus, high and rugged mountains, deep river gorges
and vast plains.
In Ethiopia, Altitude ranges from 125 meters below sea level (Kobar Sink) to the
highest mountain in Ethiopia, Mount Ras Dashen (4,620 m.a.s.l), which is the
fourth highest mountain in Africa.
Ethiopia has the largest proportion of elevated landmass in the African continent.
It is sometimes described as the Roof of East Africa because of its height and large
area.
Proportion of Ethiopian lands above 1,000 meters of is 50% of the total and
Proportion of land above 1,500 meters is about 44% of the country.
2

3. Ethiopian Topography

4. Half of this(near 22%), in turn, is at more than 2,000 meters above sea level.
Most of the Ethiopian Highlands are part of central and northern Ethiopia,
and its northernmost portion extends into Eritrea.
The highland core, on the other hand, is encircled by semi-arid and lowlands.
The Ethiopian Highlands are rugged mass of mountains, situated in the Horn
of Africa.
They are the most significant physical features of the country, which form the
largest continuous area of its elevation in the continent.
They have been dissected by several rivers and ravines which have cut deep
gorges.

5. They have been divided into several regions and mountain systems.
Most of the country consists of high plateau and mountain ranges that are
sources of many rivers and streams that made the country to be described as
the “Water Tower of East Africa”.
The diversity in topography is accompanied by differences in other natural
features such as soil, climate, vegetation and wild life.
Likewise, the socio-cultural and economic phenomena are also affected by the
topography.
If 1,000 meters contour line for is taken as highland-lowland demarcation
line, one can observes the following contrasting features between the
Ethiopian highlands and lowlands:

6. Features /Characteristics of Ethiopian highlands:
o Moderate and high amount of rainfall (> 600 mm per year).
o Lower mean annual temperature (< 200C)
o The climate is favorable for biotic life.
o Rain-fed agriculture is possible.
o Free from tropical diseases.
o Attractive for human habitation and densely settled.
o The cumulative effect of all this is that, the highlands have been
significant throughout Ethiopian history in the economic, cultural
and political life of the people.

7.  These highlands make up nearly 56% of the area of the Ethiopia.
 This is further subdivided into:
o Lower highland (1,000 - 2,000 m.a.s.l), which make up 35%
o Higher highland (>2,000 m.a.s.l) constituting nearly 22%.
Features /Characteristics of Ethiopian lowlands:
o Fewer amounts of rainfall and higher temperature.
o High prevalence of tropical diseases( malaria, cholera, chagas disease, yellow fever,
and dengue)
o Lower population densities.
o Nomadic and semi-nomadic economic life.
o Vast plain lands favorable for irrigation agriculture along the lower river basins.
 The remaining 35% of the area of the Ethiopia is lowland.

8.  Following the structural divisions brought about by the geologic
processes of the Cenozoic Era, three major physiographic units can
be identified in Ethiopia.
These are:
1. The Western highlands and lowlands
2. The South-eastern (Eastern) highlands and lowlands
3. The Rift Valley

9. 3.2.1. The Western Highlands and Lowlands
This physiographic unit includes all the area west of the Rift Valley.
It extends from northern most point of Tigray to the ethio-kenyan boarder in
the south encompassing nearly the whole western half of Ethiopia.
It makes up about 44% of the area of the country.
In the east the western escarpment of the Rift Valley bound it whereas
westward, the land gradually descends in altitude until it merges into the
western foothills and lowlands, along the Sudan and South Sudan border.
This region is further subdivided into
o Four groups of highlands (76.3%) and
o Four groups of lowlands (23.7%)

10. A. The Tigray Plateau
 It extends from the Tekeze gorge in the south to central Eritrean highlands.
 The Tigray plateau is separated from the Eritrean plateau by the Mereb
River.
 It lies to the southeast of the upper course of the Mereb/Gash River and to
the northeast of Tekeze River Gorge.
 It constitutes about 13% of the area of the region.
 It is an elongated highland with most of the land being in between 1,000
and 2,000 meters above sea level.

12. …
 The right bank tributaries of Tekeze drain this plateau. Long period of
denudation has created residual features of granite hills, rugged topography,
and Ambas.
 There are high mountains in this plateau with elevations of over 3000 meters,
namely Mount Tsibet (3988 m.a.s.l), Mount Ambalage (3291 m.a.s.l), and
Mount Assimba (3248 m.a.s.l).
 The famous monastery at Debre-Damo, a tableland that can only be climbed
by a rope pulley is also located in this plateau region.

13. B. North Central Massifs
This Physiographic division is the largest in the western highlands.
Much of its northern and southern limit follows the Abay and Tekeze gorges.
The Abay, Tekeze and their tributaries have cut into this region a maze of gorges,
steep sided river valleys, dividing the land into many isolated plateau blocks,
precipitous tablelands and other rugged surface forms.
But much of these plateau and tablelands are still capped by the Trappean lava.
In its central part, the physiographic unit also accommodates the Lake Tana basin
surrounded by plains of Fogera and Dembia in the north and an upland plain in its
south.
Fifty-eight percent of the region is at an altitude of more than 2,000 meters, making
it, next to the Shewan Plateau, the second highest physiographic division.
The region consists of the Gonder, Wello and Gojjam Massifs.

14. …
Out of the 26 mountain peaks with altitude of more than 4,000m.a.s.l in Ethiopia,
19 mountain peaks are found in this physiographic region.
Among these, the most popular ones include Mount Ras Dashen (4,620 m.a.s.l),
Mount Weynobar/Ancua (4462 m.a.s.l), Mount KidisYared (4453 m.a.s.l), and
Mount Bwahit (4437 m.a.s.l) in the Simen Mountain System.
Mount Guna (4,231m.a.s.l) in the Debre Tabour Mountain System, Abune Yoseph
(4,260 m.a.s.l) in the Lasta highlands of Wello and Mount Birhan (4,154 m.a.s.l) in
the Choke Mountain System in Gojjam are also part of Simen Mountain System.
These mountains have steep cliffs and rugged terrain that provide scenic views
to climbers.

15. …
 The Mountain systems in Gonder and Gojjam are separated from the eastern
group of mountains in Wello by impenetrable and deep gorges.
 At one point though, they are connected by Yeju-Wadla Delanta land
bridge (ridge).
 This land bridge has been significant in history.
 It served as a route of penetration by the Turks, Portuguese, and Italians etc.
 The Woreta-Debre Tabor-Woldya road constructed to link the northwestern region
with Asseb through Woldya and Dessie took advantage of this land bridge

16. C. The Shewa Plateau/central highlands
The Shewan plateau is bounded by the Rift Valley in the east and
southeast, by the Abay gorge in its northern and western limit, and the
Omo gorge in the south and west.
This plateau occupies a central geographical position in Ethiopia.
With only 11% of the area of the whole physiographic region, the Shewa
Plateau is the smallest of the Western highlands.
Nearly three-fourth of its area is at an altitude of more than 2,000 meters
above sea level.
It has, therefore, the largest proportion of elevated ground.

17. …
The Shewa plateau is drained, outward in all directions by the tributaries of
Abay, Omo, and Awash.
 It, therefore, forms a water divide for these three river basins.
The tributaries of Abay-Guder, Muger, Jema etc. have cut deep gorges and
steep sided river valleys.
They have created several tablelands and isolated plateau units in the north.
Similarly, the tributaries of Omo and Awash have dissected the other sides of
the plateau. Otherwise, this plateau has relatively extensive flat-topped
uplands, giving it the appearance of a true plateau.
 The highest mountain in the Shewan plateau is Mount Abuye-Meda (4,000
m.a.s.l) in Northern Shewa, Mount Guraghe in the south is 3,721 meters high.

18. D. The Southwestern Highlands
 This Physiographic subdivision consists of the highlands of Wellega, Illuababora, Jimma, Kaffa,
Gamo and Gofa.
 This region is separated from the adjacent highlands by the Abay and Omo river valleys.
 It extends from the Abay gorge in the north to the Kenya border and Chew Bahir in the south.
 It accounts for 22.7% of the area of the region.
 The region is the second largest in the Western highlands.
 About 70% of its area is lies within 1,000-2,000 meters altitude.
 The southwestern plateau is the. wettest in Ethiopia
 It is drained by Dabus, Deddessa (tributaries of Abay), Baro, Akobo and the Ghibe/Omo rivers.
 It is also the home of most numerous and diverse ethnic linguistic groups in Ethiopia.
 With a height of 4,200 meters above sea level, Guge Mountain is the highest peak in this
physiographic subdivision.

19.  These are the western foothills and border plains that extend from Western
Tigray in the north to southern Gamo-Gofa in the South.
 In certain places, ridges or part of the highlands protrude into the lowlands,
interrupting their continuity.
 They make 11% of the area of the physiographic region.
 The general elevation ranges between 500 and 1000 meters above sea level.
 This physiographic sub-region is further subdivided into four by the protruding
ridges. These are
 Tekeze lowland
 Setitu Humera lowland
 Abay-Dinder lowland
 Abay Drainage areas
 Baro lowland, and
 Ghibe lowland from north to south.

20. …
 With the exception of the Baro lowland, the region is generally
characterized by arid or semi-arid conditions.
 Pastoral or semi-pastoral economic activities dominate the area.
 As one moves northwards, the degree of aridity increases, making rain-fed
agriculture more difficult.
 Since one or two rivers cross all of these lowlands, irrigation agriculture is
highly feasible.
 For example, the Baro lowland has an extensive flat area suitable for mechanized
agriculture.

21. …
 The Ghibe/Omo lowland, which includes the lower Ghibe/Omo Valley and the
northern section of the Turkana basin, is classified in the Western lowlands from
its geographical location. But structurally it also belongs to the Rift Valley.
 It is an area, which is both faulted and tectonically depressed.
 In the Western lowlands, there are small but important towns. Their importance
could be related to agriculture, history, or are simply border towns and frontier
ports.
 These are Humera, Metema, Omedla, Kurmuk, Gambella etc

22. 3.2.2. The Southeastern Highlands and Lowlands
is the second largest in terms of area.
 It accounts for 37% of the area of Ethiopia.
The highlands make up 46% of the physiographic division while the rest
is lowland.
In the west and north, the eastern escarpment of the Rift Valley makes the
western and northern limit.
 In many places the land raises so abruptly that from the edge of the
plateau one literally looks down the Rift Valley.
From here, the land gradually descends southeastward into the
southeastern lowlands and then to the plains of Somalia.
These are further subdivided into two units of highlands and two
units of extensive lowlands

23. These highlands are found to the east of the Lakes Region.
They are located in the south western section of the physiographic region.
They make up 28.5% of the area of the region and 62% of the south - Eastern
Highlands.
The Arsi-Bale Highlands are important grains producing areas with still high
potential.
The Arsi Highlands are made up of flat rolling uplands and dissected mountains.
 The well-known mountains in this area are Mount Kaka (4,180 m.a.s.l), Mount
Bada (4,139 m.a.s.l) and Mount Chilalo (4,036 m.a.s.l).
A. The Arsi-Bale-Sidama Highlands

24. …
 The Bale highlands are separated from the Arsi highlands by the head and main
stream of Wabishebelle.
⁃ They consist of a platform looking basaltic plateau in the north-
central part and high mountain massif to the south.
⁃ The Afro-Alpine summit of Senetti plateau is found on the latter
group.
⁃ The highest mountain peaks in this region are Tulu-Demtu (4,377
m.a.s.l) and Mount Batu (4,307 m.a.s.l).

25.  The Sidama Highlands are separated from the Bale Highlands by the Ghenale
river valley.
⁃ They occupy the southwestern corner of this region.
⁃ The prominent feature here is the Jemjem plateau, an important coffee
growing area.
 Rivers Wabishebelle and Ghenale along with their tributaries have dissected
this physiographic region. Specially, Weyb River, tributary of Ghenale, has cut
an underground passage (Sof Omar cave) through the Mesozoic Limestone
rocks.
⁃ The cave is found near Bale Mountains.
⁃ It is one of the World's most spectacular and extensive underground
caverns creating a magnificent view accessible only by an underground
stream.

26. This plateau is a north-easterly extension of the south-eastern highlands.
It extends from the Chercher highlands in the south-west to Jigjiga in the east.
It makes up 38% of the South Eastern highlands and 17.4% of the whole
physiographic region.
It has the smallest proportion of upper highland (>2,000 meters). It is a low
lying and elongated region.
Rising sharply from the Rift Valley floor, it immediately but gently descends
east and southeastward.
The left-bank tributaries of Wabishebelle drain it. Much of the Trappean lava is
removed and the Mesozoic rocks are extensively exposed.
The highest mountain here is Mount Gara-Muleta (3,381 m.a.s.l).

27. The Southeastern lowlands are located in the southeastern part of the country and
they are the most extensive lowlands in Ethiopia.
They make up 54% of the area of the physiographic region and around one-fifth of
the country.
They include the plains of Ogaden, Elkere, and Borena. Southeastward sloping plains
characterize these lowlands.
Because of the harsh climatic conditions, these lowlands are little used and support
very small population.
 They are sparsely inhabited by pastoral and semi-pastoral communities.
The economic potential for this region includes animal husbandry, irrigation,
agriculture and perhaps exploitation of petroleum and natural gas.

28. …
 This region is divided into Wabishebelle plain and the Ghenale Plain
 Wabe-Shebelle lowland
 Covers about 60% of the Eastern Lowlands
 Parts of Somali region and Eastern Hararghe are drained by Wabe-Shebelle river
and its tributaries
 Known for cattle, sheep, goat and camel husbandry.
Gennale Lowland
 Covers about 40% of the Eastern Lowlands
 Comprises parts of Borena and Guji lowlands which are drained by Gennale
river & its tributaries
 Known for the highest quality and quantity cattle & other domestic animals
production areas of Ethiopia due to better nourishment.

29. The Rift Valley is a tectonically formed structural depression. It is
bounded by two major and more or less parallel escarpments.
The formation of the Rift Valley has separated the Ethiopian Highlands
and Lowlands in to two. It extends from the Afar triangle in the north
to Chew Bahir for about 1,700 km2.
 It covers 18% of the area of Ethiopia. It is elongated and funnel shaped,
with a NE-SW orientation. It opens out in the Afar Triangle, where it is
the widest, and narrows down to the south.
The floor of the Rift Valley is made up of interconnected troughs,
grabens and depressions.
Volcanic rocks, fluvial and lacustrine deposits cover the floor.

30. …
In many places, numerous volcanic domes, hills and cinder cones rise from
the floor.
Altitude in the floor ranges from 125 meters below sea level at Dallol
Depression, to as high as 2,000 meters above sea level in the Lakes region.
The bounding escarpments are also of varying heights.
From the floor to the edge of the escarpment, the heights vary from 200 to
1500 meters.
Because of its altitudinal variation and positional differences, the climate also
varies from warm, hot and dry to cool and moderately moist conditions.
Similarly, the social and economic life reflects this pattern.
There are places, which are desolate and sparsely inhabited by pastoralists
where as in others parts people practice some rain-fed agriculture.

31. The Rift Valley is further subdivided into three physiographic sub-regions.
These are the Afar Triangle, the Main Ethiopian Rift, and the Chew Bahir
Rift.
I. The Afar Triangle
The Afar Triangle is the largest and widest part of the Rift Valley.
It makes up 54% of the Rift Valley area.
 It is bounded by the high western and eastern escarpments in the west and
east respectively, and by the Afar and Aisha Horst in the northeast.
The area is generally of low altitude (300-700 meters).
Quite different is the morphology of the Afar depression, triangular-shape
lowland, where elevation drops uniformly from approximately 1,000 meters
in the southwest to below sea level in the north (Danakil depression)
The depression, which hosts one of the most hostile environments on Earth

32. …
The area is characterized by faulted depressions (grabens), volcanic hills, active
volcanoes, volcanic ridges, lava fields and low lava platforms.
Lakes (Abe, Asale, and Afrera) occupy some of these basins.
 A prominent feature in this region is the Denakil Depression (Kobar Sink).
Separated from the Red Sea by a 200 meters high land barrier, much of it lies below
sea level.
A larger part of this is covered by thick and extensive salt plain.
Lake Asale and Lake Afrera occupy the lowest parts of this sunken depression.
The Afar Triangle is generally hot and dry.
The only respite one gets in the Southern part is from the waters of the Awash River.
The economic importance of this region includes salt extraction, irrigation along the
Awash River and electric potential from geothermal energy.

33. ii. The Main Ethiopian Rift/Central Rift
 It refers to the narrow belt of the Rift Valley that extends from Awash River in
the north to Lake Chamo in the south.
 It is bounded by the western and eastern escarpments.
 With the exception of the Arbaminch area, the bounding escarpments are
generally low.
 This part of the Rift Valley is the narrowest and the highest.
 It has an average width of 50-80 kilometers and general elevation of 1,000-
2,000 meters above sea level.

34. …
 The floor in many places is dotted by cinder cones and volcanic mountains.
 The big ones include Mount Fentale, Boseti-guda (near Adama), Aletu (north of
Lake Ziway) and Chebi (north of Lake Hawasa).
 The northern section has more of these cinder cones and lava fields.
 The prominent features, however, are the numerous lakes formed on tectonic
sags and fault depressions.
 Because of altitude, the lakes region of the Main Ethiopian Rift is generally
milder and watery.
 Here rain-fed agriculture is practiced.
 Other resource bases include the recreational value of the lakes, the
agricultural importance of some streams and lakes, and the geothermal
energy potential.

35. …
iii. The Chew Bahir Rift
 is the smallest and the southern-most part of the Rift Valley.
 Gneissic highlands of Konso and the surrounding highlands separate it
from the Main Ethiopian Rift to the north.
 The characteristic feature of this region is the broad and shallow
depression, which is a marshy area covered by tall grass, into which the
Segen and Woito streams empty.

36.  The highly dissected character of the landscape over much of the country's
territory along with the limited extent to which flat surfaces are present influence
the various socioeconomic aspects of Ethiopia
1. Agricultural practices
Choice of farming techniques and farm implements are highly influenced by
relief as in rugged terrain mechanized farming techniques are difficult to
practice.
Relief influences crop production as some corps are well adapted to higher
altitudes (barley, wheat) and others to low altitude (sorghum, maize).
The practice of animal husbandry is also influenced by relief as most equines
and sheep are reared in the higher altitudes and camels and goat are well
adapted to lower altitudes

37. 2. Settlement pattern
 Highlands of Ethiopia that experience a temperate type of climatic condition that are mainly free
from most of the tropical diseases are densely settled.
 Rugged and difficult terrain hinders the development of settlement and its expansion.
 The highlands of Ethiopia are characterized by sedentary life and permanent settlements
while lowlands that are inhabited by pastoralists have temporary settlements.
3. Transportation and communication
 The highly dissected and rugged topography:
 hindered the development of internal surface transportation that resulted in the long-term
isolation of many communities.
 makes infrastructure development and maintenance costly.
 influenced TV and radio communications
 rendered rivers less navigable due to the waterfalls, deep gorges and steep cliffs.

38. 4. Hydroelectric power potential
The great difference in altitude coupled with high rainfall created suitable
conditions for a very high potential for the production of hydroelectric
power in Ethiopia
5. Socio-cultural feeling
The rugged terrain as a result of excessive surface dissection resulted in
the long-term isolation of communities that led to the occurrence of
cultural diversity.
People who live in the highlands have been identifying themselves as
degegnas (mountaineers) and those who live in the lowlands as kollegnas
(lowlanders).

39. …
6. Impacts on climate
The climate of Ethiopia is a result of the tropical position of the country and the
great altitudinal variation
Highlands with higher amount of rainfall and lower rate of evapo-transpiration
tend to be moisture surplus compared to the moisture deficit lowlands.
7. Impacts on soil
Steep mountain slopes provide low angle of rest, unstable surface materials and
subject to degradation processes and relatively form shallow and little developed
soils.
8. Impacts on natural vegetation
Relief through its effect on climate and hydrology affect the type of natural
vegetation grown in an area.